Top seed Rybarikova will play Sorana Cirstea next after the Romanian eventually prevailed over Natalia Vikhlyantseva thanks to a marathon first set tie-break, winning 7-6 (16-14) 6-4 in just over two hours.

Viktoriya Tomova looked on track for a big win against Viktorija Golubic, but the Swiss player bounced back after a slow start to triumph 4-6 6-4 6-1 and Golubic's reward will be a quarter-final meeting on Friday with Johanna Larsson, who comfortably beat Varvara Lepchenko 6-2 6-3.